Work holders for holding a workpiece while the same is being sawed by a band saw, or the like, are usually in the form of a vise having opposed jaws relatively movable toward each other for gripping the workpiece. The jaws are usually operated by a threaded shaft, pivoted linkage, expansible chamber motor, or other known actuators, and often, one jaw will be fixed with respect to the saw frame or mechanism, while the other jaw is movable theretoward.
Conventionally, work holders used in conjunction with band saws, and the like, are mounted to one side of the path of saw blade movement Thus, when sawing a rod or shaft, for instance, the rod would be mcunted within the work holder jaws and the portion to be severed would extend in a cantilever manner into the blade path of movement Such an arrangement only provides firm support of the workpiece on one side of the blade and a symmetrical retention of the workpiece with respect to the blade is not present. The asymmetrical holding forces imposed on the workpiece during sawing make it very difficult to maintain close tolerances, particularly when sawing thin sections from a rod, shaft, or the like. Further, as the workpiece is gripped at a location laterally removed from the saw blade, the work will often deform which, in turn, may deflect the blade from its predetermined direction of movement.
It is an object of the invention to provide a work holder for use with a saw wherein the saw blade is horizontally laterally displaced through a work table wherein the work holder produces symmetrical work holding forces on the workpiece with respect to the saw blade during sawing.
Another object of the invention is to provide a work holder for a vertical band saw wherein the work holder is mounted upon the horizontal saw table and symmetrically engages and clamps the workpiece relative to the saw blade and its direction of movement.
Yet another object of the invention is to provide a work holder for a vertical band saw having a horizontal work table wherein the saw blade is fed through a table slot, a reference member mounted upon the table intersected by the slot and blade positions the workpiece relative to the blade, and a clamp mounted upon the table includes a clamp head forcing the workpiece against the reference member, the clamp head engaging the workpiece on each side thereof with respect to the direction of blade movement.
An additional object of the invention is to provide a work holder for vertical band saws and the like wherein the workpiece is symmetrically supported relative to the direction of blade movement and close sawing tolerances may be consistently achieved.
The concepts of the invention are best practiced with a vertical band saw having a gravity feed of the band saw blade, although it is appreciated that the concepts can be incorporated into similar apparatus wherein a blade is advanced into a workpiece supported upon a table.
In a vertical gravity feed band saw the saw includes a horizontal table having a slot defined therein. The band saw blade is mounted upon a carriage which is inclined to the vertical which permits the blade to be fed, by gravity, through the slot into a workpiece mounted upon the saw table. Normally, the table includes a stop or abutment in alignment with the slot, and the downwardly moving portion of the blade is fed laterally in a horizontal direction through the table slot toward the workpiece resting or clamped against the abutment. The blade engages the workpiece and is fed therein by gravity forces acting on the blade carriage, and during sawing no relative movement takes place between the workpiece and work table.
In the practice of the invention an elongated reference member or fence is mounted on the work table with its length perpendicular to the blade receiving slot defined in the table. The reference member is defined by two aligned portions located on opposite sides of the slot separated by a distance only slightly greater than the blade thickness. The reference member includes a vertically oriented face against which the workpiece is clamped, and measurement indicia is preferably defined on this face. Also, an adjustable workpiece stop is associated with the reference member to facilitate sawing of predetermined lengths without independent measurement.
A clamp support is bolted to the work table in alignment with the table slot, and a clamp head is supported by the clamp support upon an elongated rod for adjustment toward and away from the reference member. Preferably, the rod is in alignment with the table slot, and the clamp head is mounted on the rod outer end.
The clamp head is slidably supported upon the work table by a friction reducing pad, and the head includes a face in opposed relationship to the reference member face. The clamp head is of sufficient horizontal width in a direction transverse to the table slot wherein the head face "bridges" the table slot, substantially equal portions of the head being located upon each side of the slot.
The workpiece is placed upon the work table adjacent the reference member, and the clamp head is brought against the workpiece to force the workpiece against the reference member and thereby rigidly clamp the workpiece upon the table. A lock defined on the clamp support locks the position of the rod and clamp head relative to the clamp support, and in this manner, the workpiece is firmly held upon the work table between the reference member and the clamp head. The saw blade is then permitted to pass through the reference member and engage the workpiece, and the saw will feed into the workpiece. Movement of the saw blade is continued until the blade engages the clamp head, and at that time, the workpiece will have been severed and the direction of the movement of the blade is reversed to withdraw the blade from the table slot.
As the clamp head bridges the table slot, such that the clamp head face is located upon both sides of the blade during sawing, there is no tendency for the workpiece to "tilt" with respect to the direction of the movement of the blade, and symmetrical holding forces on the workpiece are produced with respect to the blade and the forces imposed on the workpiece by the blade. Thus, with the work holder of the invention there is no tendency for the workpiece to tilt or cock with respect to the direction of blade movement and very accurate sawing tolerances can be consistently achieved.